The invention discloses an external cavity semiconductor laser array coherent beam combination method, and belongs to the technical field of semiconductor laser array coherent beam combination. According to the method, a diffraction optical element and the like are used for controlling the self-reproduction mode in a semiconductor outer cavity to be an Ermigauss mode, so that the phase locking inthe semiconductor outer cavity is achieved. Therefore, the output in the phase locking coherent mode under the high-power condition is achieved. According to the technical scheme of the invention, thecoherent beam combining method based on the Ermian Gaussian beam can provide better noise suppression capability, and the mode uniformity is high. Therefore, the coherent laser output power can be improved. Meanwhile, no extra loss is generated in the resonant cavity, and the peak of each Ermigauss beam can be directly coupled into a single light-emitting unit. Various methods for controlling generation of the Ermigauss beams in the cavity are adopted, and diffractive optical elements are adopted mostly. As a result, the method is simple and convenient to implement and low in cost. In addition, the invention also discloses an external cavity semiconductor laser array coherent beam combining device.